Electrical appliances often include motors or pumps that, during operation, transfer vibrational motion to other connected components of the appliance. For example, laundry clothes washing machines usually incorporate a pump for removing soil- or detergent-containing water from a laundry load within an outer bowl (also known as a washtub). The removed water may be recirculated back into the outer bowl or may be expelled to a drain. In the case of a laundry washing machine of the “top-loading” or “vertical-axis” variety the pump may be attached beneath the outer bowl, directly to the base of the outer bowl via a mounting arrangement. During operation of the pump, vibrations generated by the rotation of the rotor and impeller of the pump are transmitted through the mounting arrangement to the outer bowl and may also be transmitted to the cabinet or “wrapper” of the machine via the suspension system and other attachment points. Such vibrations of the outer bowl and/or the cabinet, which have a much larger surface area than the pump or are resonantly excitable parts, can result in unwanted audible noise.
It is known to provide a damping arrangement between the pump and the outer bowl to reduce the amplitude of the transmitted vibrations. Such known damping arrangements utilise compressible rubber or elastomeric washers or spacers surrounding fasteners connecting the pump (or a mounting bracket holding the pump) to the base of the outer bowl. Whilst such washers/spacers reduce transmitted vibrations to the body of the appliance, in some cases their effectiveness only reaches an acceptable level when the volume of compressible material, and therefore the axial spacing between the pump/bracket and the base of the outer bowl, is increased to a sufficiently large value. In many modern home appliances, such as laundry clothes washing machines, space within the cabinet is at a premium and often it is desirable to minimise the distance between the base of the outer bowl and the pump/bracket.
It is also known to utilise dampers comprising a solid, for example a metal such as brass, “crush” tube surrounded by a compressible rubber or elastomeric material disk to dampen vibrations between the pump and outer bowl. The crush tube has a central hole through which the fastener passes and the rubber/elastomeric disk has a thickness comparable to the axial length of the crush tube with an annular circumferential groove in an outer cylindrical face. This type of damper must be mounted to a hole in a flange of a pump bracket by being pushed through a slot in the edge of the flange. It will be appreciated that this type of damper necessarily has a relatively large outer diameter, as well as a significant axial length, and so takes up a relatively large spatial volume on and around the mounting bracket. Such a requirement places restrictions on the design and layout of the pump bracket.
It would therefore be desirable to utilise an axially shorter vibration damping arrangement that still achieves acceptable vibration isolation results.
It is therefore an object of the present invention to provide a vibration isolator, a vibration-isolating mounting arrangement, a mounting bracket or an electrical appliance which will go at least some way towards overcoming the above disadvantages, or which will at least provide the public or industry with a useful choice.